System and method for signaling and data tunneling in a peer-to-peer environment

ABSTRACT

An improved system and method are disclosed for peer-to-peer communications. In one example, the method enables an endpoint to use a tunneling server to bypass a network address translation (NAT) device that is blocking messages to an endpoint on the other side of the NAT device.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 12/858,232, filed Aug. 17, 2010, entitled SYSTEM AND METHOD FORSIGNALING AND DATA TUNNELING IN A PEER-TO-PEER ENVIRONMENT, which is acontinuation-in-part of U.S. patent application Ser. No. 12/705,925,filed Feb. 15, 2010, entitled SYSTEM AND METHOD FOR STRATEGIC ROUTING INA PEER-TO-PEER ENVIRONMENT, now U.S. Pat. No. 8,725,895, issued May 13,2014, which are incorporated herein by reference in their entirety.

BACKGROUND

Current packet-based communication networks may be generally dividedinto peer-to-peer networks and client/server networks. Traditionalpeer-to-peer networks support direct communication between variousendpoints without the use of an intermediary device (e.g., a host orserver). Each endpoint may initiate requests directly to other endpointsand respond to requests from other endpoints using credential andaddress information stored on each endpoint. However, becausetraditional peer-to-peer networks include the distribution and storageof endpoint information (e.g., addresses and credentials) throughout thenetwork on the various insecure endpoints, such networks inherently havean increased security risk. While a client/server model addresses thesecurity problem inherent in the peer-to-peer model by localizing thestorage of credentials and address information on a server, adisadvantage of client/server networks is that the server may be unableto adequately support the number of clients that are attempting tocommunicate with it. As all communications (even between two clients)must pass through the server, the server can rapidly become a bottleneckin the system.

Accordingly, what is needed are a system and method that addresses theseissues.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding, reference is now made to thefollowing description taken in conjunction with the accompanyingDrawings in which:

FIG. 1 is a simplified network diagram of one embodiment of a hybridpeer-to-peer system.

FIG. 2a illustrates one embodiment of an access server architecture thatmay be used within the system of FIG. 1.

FIG. 2b illustrates one embodiment of an endpoint architecture that maybe used within the system of FIG. 1.

FIG. 2c illustrates one embodiment of components within the endpointarchitecture of FIG. 2b that may be used for cellular networkconnectivity.

FIG. 2d illustrates a traditional softswitch configuration with twoendpoints.

FIG. 2e illustrates a traditional softswitch configuration with threeendpoints and a media bridge.

FIG. 2f illustrates one embodiment of the present disclosure with twoendpoints, each of which includes a softswitch.

FIG. 2g illustrates one embodiment of the present disclosure with threeendpoints, each of which includes a softswitch.

FIG. 3a is a sequence diagram illustrating the interaction of variouscomponents of FIG. 2b when placing a call.

FIG. 3b is a sequence diagram illustrating the interaction of variouscomponents of FIG. 2b when receiving a call.

FIG. 4 is a sequence diagram illustrating an exemplary process by whichan endpoint of FIG. 1 may be authenticated and communicate with anotherendpoint.

FIG. 5 is a sequence diagram illustrating an exemplary process by whichan endpoint of FIG. 1 may determine the status of another endpoint.

FIG. 6 is a sequence diagram illustrating an exemplary process by whichan access server of FIG. 1 may aid an endpoint in establishingcommunications with another endpoint.

FIG. 7 is a sequence diagram illustrating an exemplary process by whichan endpoint of FIG. 1 may request that it be added to the buddy list ofanother endpoint that is currently online.

FIG. 8 is a sequence diagram illustrating an exemplary process by whichan endpoint of FIG. 1 may request that it be added to the buddy list ofanother endpoint that is currently offline.

FIG. 9 is a sequence diagram illustrating an exemplary process by whichan endpoint of FIG. 1 may request that it be added to the buddy list ofanother endpoint that is currently offline before it too goes offline.

FIG. 10 is a simplified diagram of another embodiment of a peer-to-peersystem that includes a stateless reflector that may aid an endpoint intraversing a NAT device to communicate with another endpoint.

FIG. 11 is a table illustrating various NAT types and illustrativeembodiments of processes that may be used to traverse each NAT typewithin the system of FIG. 10.

FIG. 12 is a sequence diagram illustrating one embodiment of a processfrom the table of FIG. 11 in greater detail.

FIG. 13 illustrates one embodiment of a modified packet that may be usedwithin the process of FIG. 12.

FIGS. 14-18 are sequence diagrams that each illustrate an embodiment ofa process from the table of FIG. 11 in greater detail.

FIGS. 19A and 19B are simplified diagrams of another embodiment of apeer-to-peer system that includes multiple possible routes betweenendpoints.

FIG. 20 is a sequence diagram illustrating one embodiment of a processthat may be executed by endpoints within the system of FIGS. 19A and19B.

FIG. 21 is a sequence diagram illustrating one embodiment of steps fromthe sequence diagram of FIG. 20 in greater detail.

FIG. 22 is a flow chart illustrating one embodiment of a method that maybe executed by an endpoint within the system of FIGS. 19A and 19B.

FIGS. 23A and 23B are simplified diagrams of another embodiment of apeer-to-peer system that includes a tunneling server and multiplepossible routes between endpoints.

FIG. 24 is a sequence diagram illustrating one embodiment of a processthat may be executed by endpoints within the system of FIGS. 23A and23B.

FIG. 25 is a simplified diagram of another embodiment of a peer-to-peersystem that includes a tunneling server and multiple tunnels between thetunneling server and various endpoints.

FIG. 26 is a sequence diagram illustrating one embodiment of a processthat may be executed within the system of FIG. 25.

FIG. 27 is a simplified diagram of another embodiment of thepeer-to-peer system of FIG. 25 illustrating one of the tunnels of FIG.25 as multiple tunnels.

FIG. 28 is a flow chart illustrating one embodiment of a method that maybe executed by the tunneling server within the system of FIG. 25.

FIGS. 29A and 29B are simplified diagrams of embodiments of thepeer-to-peer system of FIG. 25 illustrating possible connectionconfigurations.

FIG. 30 is a simplified diagram of one embodiment of a computer systemthat may be used in embodiments of the present disclosure.

DETAILED DESCRIPTION

The present disclosure is directed to a system and method forpeer-to-peer hybrid communications. It is understood that the followingdisclosure provides many different embodiments or examples. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. In addition, the present disclosure mayrepeat reference numerals and/or letters in the various examples. Thisrepetition is for the purpose of simplicity and clarity and does not initself dictate a relationship between the various embodiments and/orconfigurations discussed.

Referring to FIG. 1, one embodiment of a peer-to-peer hybrid system 100is illustrated. The system 100 includes an access server 102 that iscoupled to endpoints 104 and 106 via a packet network 108. Communicationbetween the access server 102, endpoint 104, and endpoint 106 isaccomplished using predefined and publicly available (i.e.,non-proprietary) communication standards or protocols (e.g., thosedefined by the Internet Engineering Task Force (IETF) or theInternational Telecommunications Union-Telecommunications StandardSector (ITU-T)). For example, signaling communications (e.g., sessionsetup, management, and teardown) may use a protocol such as the SessionInitiation Protocol (SIP), while actual data traffic may be communicatedusing a protocol such as the Real-time Transport Protocol (RTP). As willbe seen in the following examples, the use of standard protocols forcommunication enables the endpoints 104 and 106 to communicate with anydevice that uses the same standards. The communications may include, butare not limited to, voice calls, instant messages, audio and video,emails, and any other type of resource transfer, where a resourcerepresents any digital data. In the following description, media trafficis generally based on the user datagram protocol (UDP), whileauthentication is based on the transmission control protocol/internetprotocol (TCP/IP). However, it is understood that these are used forpurposes of example and that other protocols may be used in addition toor instead of UDP and TCP/IP.

Connections between the access server 102, endpoint 104, and endpoint106 may include wireline and/or wireless communication channels. In thefollowing description, it is understood that the term “direct” meansthat there is no endpoint or access server in the communicationchannel(s) between the endpoints 104 and 106, or between either endpointand the access server. Accordingly, the access server 102, endpoint 104,and endpoint 106 are directly connected even if other devices (e.g.,routers, firewalls, and other network elements) are positioned betweenthem. In addition, connections to endpoints, locations, or services maybe subscription based, with an endpoint only having access if theendpoint has a current subscription. Furthermore, the followingdescription may use the terms “user” and “endpoint” interchangeably,although it is understood that a user may be using any of a plurality ofendpoints. Accordingly, if an endpoint logs in to the network, it isunderstood that the user is logging in via the endpoint and that theendpoint represents the user on the network using the user's identity.

The access server 102 stores profile information for a user, a sessiontable to track what users are currently online, and a routing table thatmatches the address of an endpoint to each online user. The profileinformation includes a “buddy list” for each user that identifies otherusers (“buddies”) that have previously agreed to communicate with theuser. Online users on the buddy list will show up when a user logs in,and buddies who log in later will directly notify the user that they areonline (as described with respect to FIG. 4). The access server 102provides the relevant profile information and routing table to each ofthe endpoints 104 and 106 so that the endpoints can communicate directlywith one another. Accordingly, in the present embodiment, one functionof the access server 102 is to serve as a storage location forinformation needed by an endpoint in order to communicate with otherendpoints and as a temporary storage location for requests, voicemails,etc., as will be described later in greater detail.

With additional reference to FIG. 2a , one embodiment of an architecture200 for the access server 102 of FIG. 1 is illustrated. The architecture200 includes functionality that may be provided by hardware and/orsoftware, and that may be combined into a single hardware platform ordistributed among multiple hardware platforms. For purposes ofillustration, the access server in the following examples is describedas a single device, but it is understood that the term applies equallyto any type of environment (including a distributed environment) inwhich at least a portion of the functionality attributed to the accessserver is present.

In the present example, the architecture includes web services 202(e.g., based on functionality provided by XML, SOAP, .NET, MONO), webserver 204 (using, for example, Apache or IIS), and database 206 (using,for example, mySQL or SQLServer) for storing and retrieving routingtables 208, profiles 210, and one or more session tables 212.Functionality for a STUN (Simple Traversal of UDP through NATs (NetworkAddress Translation)) server 214 is also present in the architecture200. As is known, STUN is a protocol for assisting devices that arebehind a NAT firewall or router with their packet routing. Thearchitecture 200 may also include a redirect server 216 for handlingrequests originating outside of the system 100. One or both of the STUNserver 214 and redirect server 216 may be incorporated into the accessserver 102 or may be a standalone device. In the present embodiment,both the server 204 and the redirect server 216 are coupled to thedatabase 206.

Referring to FIG. 2b , one embodiment of an architecture 250 for theendpoint 104 (which may be similar or identical to the endpoint 106) ofFIG. 1 is illustrated. It is understood that that term “endpoint” mayrefer to many different devices having some or all of the describedfunctionality, including a computer, a VoIP telephone, a personaldigital assistant, a cellular phone, or any other device having an IPstack upon which the needed protocols may be run. Such devices generallyinclude a network interface, a controller coupled to the networkinterface, a memory coupled to the controller, and instructionsexecutable by the controller and stored in the memory for performing thefunctions described in the present application. Data needed by anendpoint may also be stored in the memory. The architecture 250 includesan endpoint engine 252 positioned between a graphical user interface(GUI) 254 and an operating system 256. The GUI 254 provides user accessto the endpoint engine 252, while the operating system 256 providesunderlying functionality, as is known to those of skill in the art.

The endpoint engine 252 may include multiple components and layers thatsupport the functionality required to perform the operations of theendpoint 104. For example, the endpoint engine 252 includes a softswitch258, a management layer 260, an encryption/decryption module 262, afeature layer 264, a protocol layer 266, a speech-to-text engine 268, atext-to-speech engine 270, a language conversion engine 272, anout-of-network connectivity module 274, a connection from other networksmodule 276, a p-commerce (e.g., peer commerce) engine 278 that includesa p-commerce agent and a p-commerce broker, and a cellular networkinterface module 280.

Each of these components/layers may be further divided into multiplemodules. For example, the softswitch 258 includes a call control module,an instant messaging (IM) control module, a resource control module, aCALEA (Communications Assistance to Law Enforcement Act) agent, a mediacontrol module, a peer control module, a signaling agent, a fax controlmodule, and a routing module.

The management layer 260 includes modules for presence (i.e., networkpresence), peer management (detecting peers and notifying peers of beingonline), firewall management (navigation and management), mediamanagement, resource management, profile management, authentication,roaming, fax management, and media playback/recording management.

The encryption/decryption module 262 provides encryption for outgoingpackets and decryption for incoming packets. In the present example, theencryption/decryption module 262 provides application level encryptionat the source, rather than at the network. However, it is understoodthat the encryption/decryption module 262 may provide encryption at thenetwork in some embodiments.

The feature layer 264 provides support for various features such asvoice, video, IM, data, voicemail, file transfer, file sharing, class 5features, short message service (SMS), interactive voice response (IVR),faxes, and other resources. The protocol layer 266 includes protocolssupported by the endpoint, including SIP, HTTP, HTTPS, STUN, RTP, SRTP,and ICMP. It is understood that these are examples only, and that feweror more protocols may be supported.

The speech-to-text engine 268 converts speech received by the endpoint(e.g., via a microphone or network) into text, the text-to-speech engine270 converts text received by the endpoint into speech (e.g., for outputvia a speaker), and the language conversion engine 272 may be configuredto convert inbound or outbound information (text or speech) from onelanguage to another language. The out-of-network connectivity module 274may be used to handle connections between the endpoint and externaldevices (as described with respect to FIG. 12), and the connection fromother networks module 276 handles incoming connection attempts fromexternal devices. The cellular network interface module 280 may be usedto interact with a wireless network.

With additional reference to FIG. 2c , the cellular network interfacemodule 280 is illustrated in greater detail. Although not shown in FIG.2b , the softswitch 258 of the endpoint architecture 250 includes acellular network interface for communication with the cellular networkinterface module 280. In addition, the cellular network interface module280 includes various components such as a call control module, asignaling agent, a media manager, a protocol stack, and a deviceinterface. It is noted that these components may correspond to layerswithin the endpoint architecture 250 and may be incorporated directlyinto the endpoint architecture in some embodiments.

Referring to FIG. 2d , a traditional softswitch architecture isillustrated with two endpoints 282 and 284, neither of which includes asoftswitch. In the present example, an external softswitch 286 maintainsa first signaling leg (dotted line) with the endpoint 282 and a secondsignaling leg (dotted line) with the endpoint 284. The softswitch 286links the two legs to pass signaling information between the endpoints282 and 284. Media traffic (solid lines) may be transferred between theendpoints 282 and 284 via a media gateway 287.

With additional reference to FIG. 2e , the traditional softswitcharchitecture of FIG. 2d is illustrated with a third endpoint 288 thatalso does not include a softswitch. The external softswitch 286 nowmaintains a third signaling leg (dotted line) with the endpoint 288. Inthe present example, a conference call is underway. However, as none ofthe endpoints includes a softswitch, a media bridge 290 connected toeach endpoint is needed for media traffic. Accordingly, each endpointhas at most two concurrent connections—one with the softswitch forsignaling and another with the media bridge for media traffic.

Referring to FIG. 2f , in one embodiment, unlike the traditionalarchitecture of FIGS. 2d and 2e , two endpoints (e.g., the endpoints 104and 106 of FIG. 1) each include a softswitch (e.g., the softswitch 258of FIG. 2b ). Each endpoint is able to establish and maintain bothsignaling and media traffic connections (both virtual and physical legs)with the other endpoint. Accordingly, no external softswitch is needed,as this model uses a distributed softswitch method to handlecommunications directly between the endpoints.

With additional reference to FIG. 2g , the endpoints 104 and 106 areillustrated with another endpoint 292 that also contains a softswitch.In this example, a conference call is underway with the endpoint 104acting as the host. To accomplish this, the softswitch contained in theendpoint 104 enables the endpoint 104 to support direct signaling andmedia traffic connections with the endpoint 292. The endpoint 104 canthen forward media traffic from the endpoint 106 to the endpoint 292 andvice versa. Accordingly, the endpoint 104 may support multipleconnections to multiple endpoints and, as in FIG. 2f , no externalsoftswitch is needed.

Referring again to FIG. 2b , in operation, the softswitch 258 usesfunctionality provided by underlying layers to handle connections withother endpoints and the access server 102, and to handle services neededby the endpoint 104. For example, as is described below in greaterdetail with respect to FIGS. 3a and 3b , incoming and outgoing calls mayutilize multiple components within the endpoint architecture 250.

Referring to FIG. 3a , a sequence diagram 300 illustrates an exemplaryprocess by which the endpoint 104 may initiate a call to the endpoint106 using various components of the architecture 250. Prior to step 302,a user (not shown) initiates a call via the GUI 254. In step 302, theGUI 254 passes a message to the call control module (of the softswitch258) to make the call. The call control module contacts the peer controlmodule (softswitch 258) in step 304, which detects the peer (if notalready done), goes to the routing table (softswitch 258) for therouting information, and performs similar operations. It is understoodthat not all interactions are illustrated. For example, the peer controlmodule may utilize the peer management module (of the management layer260) for the peer detection. The call control module then identifies aroute for the call in step 306, and sends message to the SIP protocollayer (of the protocol layer 266) to make the call in step 308. In step310, the outbound message is encrypted (using the encryption/decryptionmodule 262) and the message is sent to the network via the OS 256 instep 312.

After the message is sent and prior to receiving a response, the callcontrol module instructs the media control module (softswitch 258) toestablish the needed near-end media in step 314. The media controlmodule passes the instruction to the media manager (of the managementlayer 260) in step 316, which handles the establishment of the near-endmedia.

With additional reference to FIG. 3b , the message sent by the endpoint104 in step 312 (FIG. 3a ) is received by the endpoint 106 and passedfrom the OS to the SIP protocol layer in step 352. The message isdecrypted in step 354 and the call is offered to the call control modulein step 356. The call control module notifies the GUI of an incomingcall in step 358 and the GUI receives input identifying whether the callis accepted or rejected (e.g., by a user) in step 360. In the presentexample, the call is accepted and the GUI passes the acceptance to thecall control module in step 362. The call control module contacts thepeer control module in step 364, which identifies a route to the callingendpoint and returns the route to the call control module in step 366.In steps 368 and 370, the call control module informs the SIP protocollayer that the call has been accepted and the message is encrypted usingthe encryption/decryption module. The acceptance message is then sent tothe network via the OS in step 372.

In the present example, after the call control module passes theacceptance message to the SIP protocol layer, other steps may occur toprepare the endpoint 106 for the call. For example, the call controlmodule instructs the media control module to establish near-end media instep 374, and the media control module instructs the media manager tostart listening to incoming media in step 376. The call control modulealso instructs the media control module to establish far-end media (step378), and the media control module instructs the media manager to starttransmitting audio in step 380.

Returning to FIG. 3a , the message sent by the endpoint 106 (step 372)is received by the OS and passed on to the SIP protocol layer in step318 and decrypted in step 320. The message (indicating that the call hasbeen accepted) is passed to the call control module in step 322 and fromthere to the GUI in step 324. The call control module then instructs themedia control module to establish far-end media in step 326, and themedia control module instructs the media manager to start transmittingaudio in step 328.

The following figures are sequence diagrams that illustrate variousexemplary functions and operations by which the access server 102 andthe endpoints 104 and 106 may communicate. It is understood that thesediagrams are not exhaustive and that various steps may be excluded fromthe diagrams to clarify the aspect being described.

Referring to FIG. 4 (and using the endpoint 104 as an example), asequence diagram 400 illustrates an exemplary process by which theendpoint 104 may authenticate with the access server 102 and thencommunicate with the endpoint 106. As will be described, afterauthentication, all communication (both signaling and media traffic)between the endpoints 104 and 106 occurs directly without anyintervention by the access server 102. In the present example, it isunderstood that neither endpoint is online at the beginning of thesequence, and that the endpoints 104 and 106 are “buddies.” As describedabove, buddies are endpoints that have both previously agreed tocommunicate with one another.

In step 402, the endpoint 104 sends a registration and/or authenticationrequest message to the access server 102. If the endpoint 104 is notregistered with the access server 102, the access server will receivethe registration request (e.g., user ID, password, and email address)and will create a profile for the endpoint (not shown). The user ID andpassword will then be used to authenticate the endpoint 104 during laterlogins. It is understood that the user ID and password may enable theuser to authenticate from any endpoint, rather than only the endpoint104.

Upon authentication, the access server 102 updates a session tableresiding on the server to indicate that the user ID currently associatedwith the endpoint 104 is online. The access server 102 also retrieves abuddy list associated with the user ID currently used by the endpoint104 and identifies which of the buddies (if any) are online using thesession table. As the endpoint 106 is currently offline, the buddy listwill reflect this status. The access server 102 then sends the profileinformation (e.g., the buddy list) and a routing table to the endpoint104 in step 404. The routing table contains address information foronline members of the buddy list. It is understood that steps 402 and404 represent a make and break connection that is broken after theendpoint 104 receives the profile information and routing table.

In steps 406 and 408, the endpoint 106 and access server 102 repeatsteps 402 and 404 as described for the endpoint 104. However, becausethe endpoint 104 is online when the endpoint 106 is authenticated, theprofile information sent to the endpoint 106 will reflect the onlinestatus of the endpoint 104 and the routing table will identify how todirectly contact it. Accordingly, in step 410, the endpoint 106 sends amessage directly to the endpoint 104 to notify the endpoint 104 that theendpoint 106 is now online. This also provides the endpoint 104 with theaddress information needed to communicate directly with the endpoint106. In step 412, one or more communication sessions may be establisheddirectly between the endpoints 104 and 106.

Referring to FIG. 5, a sequence diagram 500 illustrates an exemplaryprocess by which authentication of an endpoint (e.g., the endpoint 104)may occur. In addition, after authentication, the endpoint 104 maydetermine whether it can communicate with the endpoint 106. In thepresent example, the endpoint 106 is online when the sequence begins.

In step 502, the endpoint 104 sends a request to the STUN server 214 ofFIG. 2. As is known, the STUN server determines an outbound IP address(e.g., the external address of a device (i.e., a firewall, router, etc.)behind which the endpoint 104 is located), an external port, and a typeof NAT used by the device. The type of NAT may be, for example, fullcone, restricted cone, port restricted cone, or symmetric, each of whichis discussed later in greater detail with respect to FIG. 10. The STUNserver 214 sends a STUN response back to the endpoint 104 in step 504with the collected information about the endpoint 104.

In step 506, the endpoint 104 sends an authentication request to theaccess server 102. The request contains the information about endpoint104 received from the STUN server 214. In step 508, the access server102 responds to the request by sending the relevant profile and routingtable to the endpoint 104. The profile contains the external IP address,port, and NAT type for each of the buddies that are online.

In step 510, the endpoint 104 sends a message to notify the endpoint 106of its online status (as the endpoint 106 is already online) and, instep 512, the endpoint 104 waits for a response. After the expiration ofa timeout period within which no response is received from the endpoint106, the endpoint 104 will change the status of the endpoint 106 from“online” (as indicated by the downloaded profile information) to“unreachable.” The status of a buddy may be indicated on a visual buddylist by the color of an icon associated with each buddy. For example,when logging in, online buddies may be denoted by a blue icon andoffline buddies may be denoted by a red icon. If a response to a notifymessage is received for a buddy, the icon representing that buddy may bechanged from blue to green to denote the buddy's online status. If noresponse is received, the icon remains blue to indicate that the buddyis unreachable. Although not shown, a message sent from the endpoint 106and received by the endpoint 104 after step 514 would indicate that theendpoint 106 is now reachable and would cause the endpoint 104 to changethe status of the endpoint 106 to online. Similarly, if the endpoint 104later sends a message to the endpoint 106 and receives a response, thenthe endpoint 104 would change the status of the endpoint 106 to online.

It is understood that other embodiments may implement alternate NATtraversal techniques. For example, a single payload technique may beused in which TCP/IP packets are used to traverse a UDP restrictedfirewall or router. Another example includes the use of a double payloadin which a UDP packet is inserted into a TCP/IP packet. Furthermore, itis understood that protocols other than STUN may be used. For example,protocols such as Internet Connectivity Establishment (ICE) or TraversalUsing Relay NAT (TURN) may be used.

Referring to FIG. 6, a sequence diagram 600 illustrates an exemplaryprocess by which the access server 102 may aid the endpoint 104 inestablishing communications with the endpoint 106 (which is a buddy).After rendering aid, the access server 102 is no longer involved and theendpoints may communicate directly. In the present example, the endpoint106 is behind a NAT device that will only let a message in (towards theendpoint 106) if the endpoint 106 has sent a message out. Unless thisprocess is bypassed, the endpoint 104 will be unable to connect to theendpoint 106. For example, the endpoint 104 will be unable to notify theendpoint 106 that it is now online.

In step 602, the endpoint 106 sends a request to the STUN server 214 ofFIG. 2. As described previously, the STUN server determines an outboundIP address, an external port, and a type of NAT for the endpoint 106.The STUN server 214 sends a STUN response back to the endpoint 106 instep 604 with the collected information about the endpoint 106. In step606, the endpoint 106 sends an authentication request to the accessserver 102. The request contains the information about endpoint 106received from the STUN server 214. In step 608, the access server 102responds to the request by sending the relevant profile and routingtable to the endpoint 106. In the present example, the access server 102identifies the NAT type associated with the endpoint 106 as being a typethat requires an outbound packet to be sent before an inbound packet isallowed to enter. Accordingly, the access server 102 instructs theendpoint 106 to send periodic messages to the access server 102 toestablish and maintain a pinhole through the NAT device. For example,the endpoint 106 may send a message prior to the timeout period of theNAT device in order to reset the timeout period. In this manner, thepinhole may be kept open indefinitely.

In steps 612 and 614, the endpoint 104 sends a STUN request to the STUNserver 214 and the STUN server responds as previously described. In step616, the endpoint 104 sends an authentication request to the accessserver 102. The access server 102 retrieves the buddy list for theendpoint 104 and identifies the endpoint 106 as being associated with aNAT type that will block communications from the endpoint 104.Accordingly, in step 618, the access server 102 sends an assist messageto the endpoint 106. The assist message instructs the endpoint 106 tosend a message to the endpoint 104, which opens a pinhole in the NATdevice for the endpoint 104. For security purposes, as the access server102 has the STUN information for the endpoint 104, the pinhole opened bythe endpoint 106 may be specifically limited to the endpoint associatedwith the STUN information. Furthermore, the access server 102 may notrequest such a pinhole for an endpoint that is not on the buddy list ofthe endpoint 106.

The access server 104 sends the profile and routing table to theendpoint 104 in step 620. In step 622, the endpoint 106 sends a message(e.g., a ping packet) to the endpoint 104. The endpoint 104 may thenrespond to the message and notify the endpoint 106 that it is nowonline. If the endpoint 106 does not receive a reply from the endpoint104 within a predefined period of time, it may close the pinhole (whichmay occur simply by not sending another message and letting the pinholetime out). Accordingly, the difficulty presented by the NAT device maybe overcome using the assist message, and communications between the twoendpoints may then occur without intervention by the access server 102.

Referring to FIG. 7, a sequence diagram 700 illustrates an exemplaryprocess by which the endpoint 106 may request that it be added to theendpoint 104's buddy list. In the present example, the endpoints 104 and106 both remain online during the entire process.

In step 702, the endpoint 104 sends a registration and/or authenticationrequest message to the access server 102 as described previously. Uponauthentication, the access server 102 updates a session table residingon the server to indicate that the user ID currently associated with theendpoint 104 is online. The access server 102 also retrieves a buddylist associated with the user ID currently used by the endpoint 104 andidentifies which of the buddies (if any) are online using the sessiontable. As the endpoint 106 is not currently on the buddy list, it willnot be present. The access server 102 then sends the profile informationand a routing table to the endpoint 104 in step 704.

In steps 706 and 708, the endpoint 106 and access server 102 repeatsteps 702 and 704 as described for the endpoint 104. The profileinformation sent by the access server 102 to the endpoint 106 will notinclude the endpoint 104 because the two endpoints are not buddies.

In step 710, the endpoint 106 sends a message to the access server 102requesting that the endpoint 104 be added to its buddy list. The accessserver 102 determines that the endpoint 104 is online (e.g., using thesession table) in step 712 and sends the address for the endpoint 104 tothe endpoint 106 in step 714. In step 716, the endpoint 106 sends amessage directly to the endpoint 104 requesting that the endpoint 106 beadded to its buddy list. The endpoint 104 responds to the endpoint 106in step 718 with either permission or a denial, and the endpoint 104also updates the access server 102 with the response in step 720. Forexample, if the response grants permission, then the endpoint 104informs the access server 102 so that the access server can modify theprofile of both endpoints to reflect the new relationship. It isunderstood that various other actions may be taken. For example, if theendpoint 104 denies the request, then the access server 102 may notrespond to another request by the endpoint 106 (with respect to theendpoint 104) until a period of time has elapsed.

It is understood that many different operations may be performed withrespect to a buddy list. For example, buddies may be deleted,blocked/unblocked, buddy status may be updated, and a buddy profile maybe updated. For block/unblock, as well as status and profile updates, amessage is first sent to the access server 102 by the endpointrequesting the action (e.g., the endpoint 104). Following the accessserver 102 update, the endpoint 104 sends a message to the peer beingaffected by the action (e.g., the endpoint 106).

Buddy deletion may be handled as follows. If the user of the endpoint104 wants to delete a contact on a buddy list currently associated withthe online endpoint 106, the endpoint 104 will first notify the accessserver 102 that the buddy is being deleted. The access server 102 thenupdates the profile of both users so that neither buddy list shows theother user as a buddy. Note that, in this instance, a unilateral actionby one user will alter the profile of the other user. The endpoint 104then sends a message directly to the endpoint 106 to remove the buddy(the user of the endpoint 104) from the buddy list of the user ofendpoint 106 in real time. Accordingly, even though the user is onlineat endpoint 106, the user of the endpoint 104 will be removed from thebuddy list of the endpoint 106

Referring to FIG. 8, a sequence diagram 800 illustrates an exemplaryprocess by which the endpoint 106 may request that it be added to theendpoint 104's buddy list. In the present example, the endpoint 104 isnot online until after the endpoint 106 has made its request.

In step 802, the endpoint 106 sends a registration and/or authenticationrequest message to the access server 102 as described previously. Uponauthentication, the access server 102 updates a session table residingon the server to indicate that the user ID currently associated with theendpoint 106 is online. The access server 102 also retrieves a buddylist associated with the user ID currently used by the endpoint 106 andidentifies which of the buddies (if any) are online using the sessiontable. The access server 102 then sends the profile information and arouting table to the endpoint 106 in step 804.

In step 806, the endpoint 106 sends a message to the access server 102requesting that the endpoint 104 be added to its buddy list. The accessserver 102 determines that the endpoint 104 is offline in step 808 andtemporarily stores the request message in step 810. In steps 812 and814, the endpoint 104 and access server 102 repeat steps 802 and 804 asdescribed for the endpoint 106. However, when the access server 102sends the profile information and routing table to the endpoint 104, italso sends the request by the endpoint 106 (including addressinformation for the endpoint 106).

In step 816, the endpoint 104 responds directly to the endpoint 106 witheither permission or a denial. The endpoint 104 then updates the accessserver 102 with the result of the response in step 818 and alsoinstructs the access server to delete the temporarily stored request.

Referring to FIG. 9, a sequence diagram 900 illustrates an exemplaryprocess by which the endpoint 106 may request that it be added to theendpoint 104's buddy list. In the present example, the endpoint 104 isnot online until after the endpoint 106 has made its request, and theendpoint 106 is not online to receive the response by endpoint 104.

In step 902, the endpoint 106 sends a registration and/or authenticationrequest message to the access server 102 as described previously. Uponauthentication, the access server 102 updates a session table residingon the server to indicate that the user ID currently associated with theendpoint 106 is online. The access server 102 also retrieves a buddylist associated with the user ID currently used by the endpoint 106 andidentifies which of the buddies (if any) are online using the sessiontable. The access server 102 then sends the profile information and arouting table to the endpoint 106 in step 904.

In step 906, the endpoint 106 sends a message to the access server 102requesting that the endpoint 104 be added to its buddy list. The accessserver 102 determines that the endpoint 104 is offline in step 908 andtemporarily stores the request message in step 910. In step 912, theendpoint 106 notifies the access server 102 that it is going offline.

In steps 914 and 916, the endpoint 104 and access server 102 repeatsteps 902 and 904 as described for the endpoint 106. However, when theaccess server 102 sends the profile information and routing table to theendpoint 104, it also sends the request by the endpoint 106. Endpoint104 sends its response to the access server 102 in step 918 and alsoinstructs the access server to delete the temporarily stored request.After the endpoint 106's next authentication process, its profileinformation will include endpoint 104 as a buddy (assuming the endpoint104 granted permission).

Referring to FIG. 10, in one embodiment, a system 1000 includes astateless reflector 1002 and two endpoints 104 and 106, such as theendpoints 104 and 106 described with respect to the preceding figures.In the present example, each of the endpoints 104 and 106 are behind adevice 1004, 1006, respectively, that monitors and regulatescommunication with its respective endpoint. Each device 1004, 1006 inthe present example is a firewall having NAT technology. As describedpreviously, a NAT device may present an obstacle in establishing apeer-to-peer connection because it may not allow unsolicited messages(e.g., it may require a packet to be sent out through the NAT devicebefore allowing a packet in). For example, the NAT device 1006positioned between the endpoint 106 and network 108 may only let amessage in (towards the endpoint 106) if the endpoint 106 has sent amessage out. Unless the NAT device's status is shifted from notsoliciting messages from the endpoint 104 to soliciting messages fromthe endpoint 104, the endpoint 104 will be unable to connect to theendpoint 106. For example, the endpoint 104 will be unable to notify theendpoint 106 that it is now online.

As will be described below in greater detail, the stateless reflector1002 is configured to receive one or more packets from an endpoint andreflect the packet to another endpoint after modifying informationwithin the packet. This reflection process enables the endpoints 104 and106 to communicate regardless of the presence and type of the NATdevices 1004 and 1006. The stateless reflector 1002 is stateless becausestate information (e.g., information relating to how an endpoint is toconnect with other endpoints) is stored by the endpoints, as describedpreviously. Accordingly, the stateless reflector 1002 processes headerinformation contained within a packet without access to otherinformation about the network or endpoints, such as the database 206 ofFIG. 2a . Although only one stateless reflector 1002 is illustrated inFIG. 10, it is understood that multiple stateless reflectors may beprovided, and that the endpoints 104 and 106 may each use a differentstateless reflector. For example, an endpoint may be configured to use aparticular stateless reflector or may select a stateless reflector basedon location, NAT type, etc.

Although each endpoint 104, 106 is shown with a separate NAT device1004, 1006, it is understood that multiple endpoints may be connected tothe network 108 via a single NAT device. For example, a LAN may accessthe network 108 via a single NAT device, and all communications betweenthe endpoints connected to the LAN and the network 108 must pass throughthe NAT device. However, communications between the endpoints within theLAN itself may occur directly, as previously described, because theendpoints are not communicating through the NAT device. Furthermore, ifone of the endpoints 104 or 106 does not have a NAT device, thencommunications with that endpoint may occur directly as described aboveeven if the endpoints are not in the same network.

Each NAT device 1004 and 1006 includes an internal IP address (on theside coupled to the endpoint 104 for the NAT device 1004 and the sidecoupled to the endpoint 106 for the NAT device 1006) and an external IPaddress (on the side coupled to the network 108 for both NAT devices).Each connection is also associated with an internal port and an externalport. Therefore, each connection includes both internal IP address/portinformation and external IP address/port information.

Generally, a NAT device may be defined as full cone, restricted cone,port restricted cone, or symmetric. A full cone NAT is one where allrequests from the same internal IP address and port are mapped to thesame external IP address and port. Therefore, any external host can senda packet to the internal host by sending a packet to the mapped externaladdress.

A restricted cone NAT is one where all requests from the same internalIP address and port are mapped to the same external IP address and port.Unlike a full cone NAT, an external host can send a packet to theinternal host only if the internal host has previously sent a packet tothe external host's IP address.

A port restricted cone NAT is like a restricted cone NAT, but therestriction includes port numbers. More specifically, an external hostcan send a packet with source IP address X and source port P to theinternal host only if the internal host has previously sent a packet tothe external host at IP address X and port P.

A symmetric NAT is one where all requests from the same internal IPaddress and port to a specific destination IP address and port aremapped to the same external IP address and port. If the same host sendsa packet with the same source address and port, but to a differentdestination, a different mapping is used. Only the external host thatreceives a packet can send a UDP packet back to the internal host.

Referring to FIG. 11, a table 1100 illustrates one embodiment of acommunication structure that may be used to traverse one or both of theNAT devices 1004 and 1006 of FIG. 10. The table 1100 provides fivepossible types for the NAT devices 1004 and 1006: no NAT, full cone,restricted cone, port restricted cone, and symmetric. It is understoodthat “no NAT” may indicate that no device is there, that a device isthere but does not include NAT functionality, or that a device is thereand any NAT functionality within the device has been disabled. Either ofthe NAT devices 1004 and 1006 may be on the originating side of thecommunication or on the terminating side. For purposes of convenience,the endpoint 104 is the originating endpoint and the endpoint 106 is theterminating endpoint, and the NAT device 1004 is the originating NATdevice and the NAT device 1006 is the terminating NAT device. It isunderstood that the terms “endpoint” and “NAT device” may be usedinterchangeably in some situations. For example, sending a packet to theendpoint 106 generally involves sending a packet to the NAT device 1006,which then forwards the packet to the endpoint 106 after performing thenetwork address translation. However, the following discussion maysimply refer to sending a packet to the endpoint 106 and it will beunderstood that the packet must traverse the NAT device 1006.

As illustrated by the table 1100, there are twenty-five possiblepairings of NAT types and establishing communication between differentNAT types may require different steps. For purposes of convenience,these twenty-five pairings may be grouped based on the required steps.For example, if the originating NAT type is no NAT, full cone,restricted cone, or port restricted cone, then the originating NAT canestablish communication directly with a terminating NAT type of eitherno NAT or full cone.

If the originating NAT type is no NAT or full cone, then the originatingNAT can establish communications with a terminating NAT type of eitherrestricted cone or port restricted cone only after using the statelessreflector 1002 to reflect a packet. This process is described below withrespect to FIG. 12.

Referring to FIG. 12, the endpoint 104 wants to inform the endpoint 106,which is already logged on, that the endpoint 104 has logged on. The NATdevice 1004 is either a no NAT or a full cone type and the NAT device1006 is either a restricted cone or a port restricted cone type.Accordingly, the endpoint 104 wants to send a message to the endpoint106, but has not received a message from the endpoint 106 that wouldallow the endpoint 104 to traverse the NAT device 1006.

Although not shown in FIG. 12, prior to or during authentication, theendpoints 104 and 106 both sent a request to a STUN server (e.g., theSTUN server 214 of FIG. 2) (not shown in FIG. 10). The STUN serverdetermined an outbound IP address, an external port, and a type of NATfor the endpoints 104 and 106 (in this example, for the NAT devices 1004and 1006). The STUN server 214 then sent a STUN response back to theendpoints 104 and 106 with the collected information. The endpoints 104and 106 then sent an authentication request to an access server (e.g.,the access server 102 of FIG. 1) (not shown in FIG. 10). The requestcontains the information about endpoints 104 and 106 received from theSTUN server 214. The access server 102 responds to the requests bysending the relevant profile and routing table to the endpoints 104 and106. In addition, each NAT device 1004 and 1006 may have a pinhole tothe STUN server 214.

In the present example, the NAT device 1004 has an external address/portof 1.1.1.1:1111 and the NAT device 1006 has an external address/port of2.2.2.2:2222. The STUN server 214 has an address/port of 3.3.3.3:3333and the stateless reflector has an address/port of 4.4.4.4:4444. It isunderstood that the STUN server and/or stateless reflector 1002 may havemultiple addresses/ports.

Referring to FIG. 12 and with additional reference to FIG. 13, in step1202, the endpoint 104 sends a packet to the stateless reflector 1002.The packet contains header information identifying the source as theendpoint 104 (or rather, the external IP address of the NAT device 1004)and the destination as the stateless reflector 1002. The packet alsocontains custom or supplemental header information identifying thesource as the STUN server 214 and the destination as the endpoint 106.Accordingly, the IP/UDP header of the packet sent from the endpoint 104(via the NAT device 1004) identifies its source as 1.1.1.1:1111 and itsdestination as 4.4.4.4:4444.

In step 1204, the stateless reflector 1002 modifies the packet header byreplacing the IP/UDP header with the source and destination from thecustom header. In the present example, the stateless reflector 1002 willmodify the IP/UDP header to identify the packet's source as 3.3.3.3:3333and its destination as 2.2.2.2:2222. Identifying the packet's source asthe STUN server 214 enables the stateless reflector 1002 to send thepacket through the pinhole in the NAT device 1006 that was created whenthe endpoint 106 logged on. After modifying the header, the statelessreflector 1002 sends the packet to the endpoint 106 via the NAT device1006 in step 1206.

In step 1208, the endpoint 106 sends an acknowledgement (e.g., a 200 OK)directly to the endpoint 104. The address of the endpoint 104 iscontained within the payload of the packet. The endpoint 106 is able tosend the acknowledgement directly because the NAT device 1004 is eithera no NAT or a full cone type. Because the endpoint 106 has opened apinhole through the restricted or port restricted NAT device 1006 to theendpoint 104 by sending a message to the endpoint 104, the endpoint 104is now able to communicate directly with the endpoint 106, as indicatedby step 1210.

Referring again to table 1100 of FIG. 11, if the originating NAT type iseither a no NAT type or a full cone type, then the originating NAT canestablish communications with a terminating NAT type that is symmetriconly after using the stateless reflector 1002 to reflect a packet andthen performing a port capture. This process is described below withrespect to FIG. 14.

Referring to FIG. 14, steps 1402, 1404, 1406, and 1408 are similar tothe reflection process described with respect to FIG. 12, and will notbe described in detail in the present example. Because the terminatingNAT type is symmetric, the originating NAT needs the port of theterminating NAT in order to send packets through the NAT device 1006.Accordingly, in step 1410, the endpoint 104 will capture the externalport used by the NAT device 1006 to send the acknowledgement in step1408. This port, along with the address of the NAT device 1006, may thenbe used when communicating with the endpoint 106, as indicated by step1412.

Referring again to table 1100 of FIG. 11, if the originating NAT type iseither a restricted cone type or a port restricted cone type, then theoriginating NAT can establish communications with a terminating NAT typethat is either restricted or port restricted by using a fake packet andthen using the stateless reflector 1002 to reflect a packet. Thisprocess is described below with respect to FIG. 15.

Referring to FIG. 15, in step 1502, the endpoint 104 sends a fake packetto the endpoint 106. Because the originating NAT type is a restrictedcone type or a port restricted cone type, the fake packet opens apinhole to the terminating NAT that will allow a response from theterminating NAT to penetrate the originating NAT. After sending the fakepacket, the sequence 1500 proceeds with steps 1504, 1506, 1508, and1510, which are similar to the reflection process described with respectto FIG. 12, and will not be described in detail in the present example.The endpoints 104 and 106 may then communicate directly, as indicated bystep 1512.

Referring again to table 1100 of FIG. 11, if the originating NAT type isa symmetric type, then the originating NAT can establish communicationswith a terminating NAT type that is either no NAT or full cone after aport capture occurs. This process is described below with respect toFIG. 16.

Referring to FIG. 16, in step 1602, the endpoint 104 (symmetric NATtype) sends a message to the endpoint 106. In step 1604, the endpoint106 captures the external port used by the NAT device 1004 in sendingthe message. This port, along with the address of the NAT device 1004,may then be used when communicating with the endpoint 104 directly, asindicated by step 1606.

Referring again to table 1100 of FIG. 11, if the originating NAT type isa restricted cone type, then the originating NAT can establishcommunications with a terminating NAT type that is symmetric by using afake packet, reflecting a packet using the stateless reflector 1002, andthen performing a port capture. This process is described below withrespect to FIG. 17.

Referring to FIG. 17, in step 1702, the endpoint 104 sends a fake packetto the endpoint 106. Because the originating NAT type is a restrictedcone type, the fake packet opens a pinhole to the terminating NAT thatwill allow a response from the terminating NAT to penetrate theoriginating NAT. After sending the fake packet, the sequence 1700proceeds with steps 1704, 1706, 1708, and 1710, which are similar to thereflection process described with respect to FIG. 12, and will not bedescribed in detail in the present example. In step 1712, the endpoint104 captures the external port used by the NAT device 1006 in sendingthe acknowledgement in step 1710. This port, along with the address ofthe NAT device 1006, may then be used when communicating with theendpoint 106 directly, as indicated by step 1714.

Referring again to table 1100 of FIG. 11, if the originating NAT type isa symmetric type, then the originating NAT can establish communicationswith a terminating NAT type that is a restricted cone type by using areflect, a fake packet, and a port capture. This process is describedbelow with respect to FIG. 18.

Referring to FIG. 18, steps 1802, 1804, and 1806 are similar to thereflection process described with respect to FIG. 12, and will not bedescribed in detail in the present example. In step 1808, in response tothe reflected message from the endpoint 104, the endpoint 106 sends afake packet to the endpoint 104. Because the terminating NAT type is arestricted cone type, the fake packet opens a pinhole to the endpoint104 to allow messages from the endpoint 104 to traverse the NAT device1006. Accordingly, in step 1810, the endpoint 104 can send the nextmessage directly to the endpoint 106 through the pinhole. In step 1812,the endpoint 106 captures the external port used by the NAT device 1004to send the message in step 1810. This port, along with the address ofthe NAT device 1004, may then be used by the endpoint 106 whencommunicating directly with the endpoint 104, as indicated by step 1814.

Referring again to table 1100 of FIG. 11, if the originating NAT type isa symmetric type and the terminating NAT type is a port restricted cone,or if the originating NAT type is a port restricted cone and theterminating NAT type is symmetric, then all signaling between the twoNAT devices is relayed via the stateless reflector 1002, while media istransferred via peer-to-peer, as described previously. If both theoriginating and terminating NAT types are symmetric, then all signalingand media are relayed via the stateless reflector 1002.

Accordingly, the peer-to-peer communications described herein may beachieved regardless of the NAT type that may be used by an endpoint. Thestateless reflector 1002 need not know the information for each client,but instead reflects various packets based on information containedwithin the packet that is to be reflected. Both the custom header andpayload may be encrypted for security purposes. However, the statelessreflector 1002 may only be able to decrypt the custom header and thepayload itself may only be decrypted by the terminating endpoint. Thisenables the stateless reflector 1002 to perform the reflectionfunctionality while maintaining the security of the payload itself. Asdescribed above, not all processes for traversing a NAT device may usethe stateless reflector 1002.

Referring to FIGS. 19A and 19B, in another embodiment, a peer-to-peerenvironment 1900 includes the two endpoints 104 and 106, the two NATdevices 1004 and 1006, and the stateless reflector 1002 of FIG. 10, andanother endpoint 1901. Also illustrated are three possible routesbetween endpoints: a private (pr) route 1902, a public (pu) route 1904,and a reflected (rl) route 1906. FIG. 19A illustrates the routes 1902,1904, and 1906 between the endpoint 104 and the endpoint 1901, and FIG.19B illustrates the routes between the endpoint 104 and the endpoint106. As will be discussed below in detail, the endpoints 104, 106, and1901 may contain logic that allows one of the three routes 1902, 1904,and 1906 to be selected in a dynamic and flexible manner rather thanrelying on the rule-based system described above.

A rule-based system may be fairly inflexible, as such a system generallyhas a clear set of rules that are defined for various NAT situations andthe current relationship between the two endpoints is handled accordingto those rules. Network configuration changes and other modificationsmay require revisions to the rules, which is not convenient and mayprevent the endpoints from communicating until the rules are revised.Accordingly, in some embodiments, the flexibility described below mayenable the endpoints 104, 106, and 1901 to adapt to new networkconfigurations without requiring updated rules as would be required in astrictly rule-based system. In still other embodiments, the logic withinthe endpoints 104, 106, and 1901 may be updated to handle new networkconfigurations, which also provides flexibility not found in strictlyrule-based systems.

Each endpoint 104, 106, and 1901 may include one or more virtualinterfaces for communication with other endpoints. In the presentexample, there are three virtual interfaces including a private virtualinterface corresponding to the private route 1902, a public virtualinterface corresponding to the public route 1904, and a relay virtualinterface corresponding to the relay route 1906. It is understood thatthe term “virtual interface” is used only for purposes of description toclarify that there are multiple possible routes. Accordingly, the term“virtual interface” need not denote separate physical network interfaceson an endpoint, but may use a single physical network interface.

As described above, each endpoint 104, 106, and 1901 is generallyassociated with two IP address/port pairs. The first IP address/portpair may be the local (i.e., private) IP address/port information thatrepresents each of the endpoints 104, 106, and 1901 in the network thatis “inside” the corresponding NAT device 1004 or 1006. For example, thefirst IP address/port pair for the endpoint 104 may be the physicaladdress assigned to the endpoint 104 by the corresponding NAT device1004. This first IP address/port pair corresponds to the private virtualinterface and may provide access via the private route to the endpoint104 by endpoints in the same local network (e.g., the endpoint 1901).The second IP address/port pair may be the public IP address/portinformation that represents each of the endpoints 104, 106, and 1901 inthe network that is “outside” the corresponding NAT device 1004 or 1006.For example, the second IP address/port pair for the endpoint 104 may bethe address that is returned to the endpoint 104 by the STUN server aspreviously described (e.g., the NAT's external IP address/port pairassigned to the endpoint 104). This second IP address/port pair for theendpoint 104 corresponds to the public virtual interface and may provideaccess via the public route to the endpoint 104 by endpoints both insideand outside the endpoint 104's local network. Each endpoint 104, 106,and 1901 is also aware of the address information of the reflector 1002as described in previous embodiments, which corresponds to the relayvirtual interface of the endpoints. The relay route may be used in(5,4), (4,5), and/or (5,5) conditions according to the table of FIG. 11,where one endpoint must send a packet first, but is unable to do sobecause the other endpoint must send a packet first.

Referring to FIG. 20, a sequence diagram illustrates one embodiment of amessage sequence 2000 that may occur between the endpoints 104 and 1901of FIG. 19A when identifying which of the routes (i.e., the privateroute 1902, the public route 1904, and the relay route 1906) will beused for communications. In the present example, the endpoints 104 and1901 are in a local (i.e., private) network such as an Enterprisenetwork, a local area network (LAN), a virtual LAN (VLAN), or a homenetwork. This local network is isolated from the public network by theNAT device 1004 or a similar network component. Although shown as asingle NAT device, it is understood that the NAT device 1004 may be aseparate NAT device for each of the endpoints 104 and 1901. In contrast,the endpoint 106 is in a separate network that is only accessible by theendpoints 104 and 1901 via a public network that forms all or part ofthe packet network 108.

The present example uses a SIP messaging model over UDP, and soaccommodates the transaction-based SIP model within connection-less UDPmessaging. Because UDP is not transaction based, certain messagehandling processes may be used to conform to SIP standards, such asdiscarding multiple messages when the SIP model expects a messagebelonging to a specific transaction. However, it is understood that thesequence 2000 may be implemented using many different messaging models.In the present example, neither endpoint is online at the beginning ofthe sequence and the endpoints 104 and 1901 are “buddies.” As describedabove, buddies are endpoints that have both previously agreed tocommunicate with one another.

In steps 2002 and 2006, the endpoints 104 and 1901, respectively, sendSTUN requests to obtain their corresponding public IP address/port pairs(NATIP, NATPort). In the present example, the reflector 1002 is servingas a STUN server, but it is understood that the STUN server may beseparate from the reflector. The reflector 1002 responds to the STUNrequests with the public IP address and port information for each of theendpoints 104 and 1901 in steps 2004 and 2008, respectively.

As the two endpoints 104 and 1901 are not logged in when the presentexample begins, they must both authenticate with the access server 102.In step 2010, the endpoint 104 sends an authentication request to theaccess server 102 with its private and public IP address/port pairs. Instep 2012, the access server 102 responds to the authentication requestand, as described previously, returns information that includes theprivate and public IP addresses of any buddy endpoints that arecurrently logged in. However, as the endpoint 1901 has not yet loggedin, the information received by the endpoint 104 from the access server102 will not include any address information for the endpoint 1901.

In step 2014, the endpoint 1901 sends an authentication request to theaccess server 102 with its private and public IP address/port pairs. Instep 2016, the access server 102 responds to the authentication requestand, as described previously, returns information that includes theprivate and public IP addresses of any buddy endpoints that arecurrently logged in. As the endpoint 104 is currently logged in, theinformation received by the endpoint 1901 from the access server 102will include the private and public address information for the endpoint104. Although not shown, the endpoint 1901 may then send a message tothe endpoint 104 informing the endpoint 104 that the endpoint 1901 iscurrently online. This message may contain the private and publicaddress information of the endpoint 1901. The message may be sent viathe three different routes as described below with respect to latermessaging, or may be sent via one or more selected routes. For example,the message may only be relayed (i.e., sent via the relay route) due tothe high chance of success of that route.

At this point, the endpoint 104 wants to establish a communicationsession with the endpoint 1901, but does not know which of the threeroutes (i.e., pr, pu, and rl) should be used. In the previouslydescribed rule-based system, the endpoint 1901 would publish its NATinformation, which enables the endpoint 104 to determine how toestablish a connection. However, in the present example, suchinformation is not published and the endpoint 104 does not know whetherthe endpoint 1901 is in the same private network as the endpoint 104,whether the endpoint 1901 is only accessible via a public network,whether the endpoint 1901 is behind a NAT device, or, if the endpoint1901 is behind a NAT device, the settings of the NAT device (full cone,port restricted, etc.). Accordingly, the endpoint 104 needs todynamically determine which of the three routes to use with the endpoint1901.

Accordingly, in step 2018, the endpoint 104 interacts with the endpoint1901 to determine which of the three routes should be used to sendmessages to the endpoint 1901. Similarly, in step 2020, the endpoint1901 interacts with the endpoint 104 to determine which of the threeroutes should be used to send messages to the endpoint 104, which maynot be the same route as that used by the endpoint 104 to send messagesto the endpoint 1901. Steps 2018 and 2020 are illustrated in greaterdetail below with respect to FIG. 21. In step 2022, the two endpointscommunicate via the determined route(s).

Referring to FIG. 21, a sequence diagram illustrates one embodiment of amessage sequence 2100 that may occur during steps 2018 and 2020 of FIG.20 in order to determine which of the routes are to be used. Theendpoint 104 may keep a table containing each buddy that is online andthe route to be used for that buddy. For example, when the route isunknown, the table may have the information shown in Table 1 below:

TABLE 1 Buddy Endpoint Route (send-receive) 1901 unk-unk X X X X

The endpoint 104 (which is the originating endpoint in the presentexample) sends out three presence messages in steps 2102, 2104, and2106. As the current example uses SIP messaging transported via UDP, themessage is a SIP INFO message. More specifically, in step 2102, theendpoint 104 sends a SIP INFO message to the private IP address/portpair of the endpoint 1901 (i.e., via the private route) with anidentifier such as a ‘pr’ tag to indicate the route. In step 2104, theendpoint 104 sends a SIP INFO message to the public (NAT) IPaddress/port pair of the endpoint 1901 (i.e., via the public route) withan identifier such as a ‘pu’ tag to indicate the route. In step 2106,the endpoint 104 sends a SIP INFO message to the endpoint 1901 via thereflector 1002 (i.e., via the relay route) with an identifier such as an‘rl’ tag to indicate the route, which is reflected to the endpoint 1901in step 2108.

The order in which the messages are sent may vary, but the order followsa hierarchy of desired routes in the present embodiment that places theprivate route first (i.e., most desirable), the public route next, andthe relay route last (i.e., least desirable). However, it is understoodthat the order in which the messages are sent may vary or, if theendpoint 104 is capable of sending multiple messages simultaneously, themessages may be sent at the same time.

The present example assumes that the endpoint 1901 receives one or moreof the messages sent in steps 2102, 2104, and 2106. If more than onemessage is received, the endpoint 1901 may respond only to the first onereceived. So, for example, if the message sent via the private route isreceived before the messages sent via the public and relay routes, theendpoint 1901 will respond only to the private route message and thelater messages will be ignored. This reduces network traffic andprovides for SIP compliance as the endpoint 104 (from a SIP perspective)expects to receive a single 200 OK message in response to its SIP INFOmessage. Furthermore, the response message may be sent back along thesame route as the presence message to which the response is directed. Soa response to the private route message will be sent back along theprivate route. Accordingly, only one of steps 2110A, 2110B, and 2110C-1may occur in the present example. Step 2110C-2 is dependent on theoccurrence of step 2110C-1 because the response message will not bereflected unless the relay route is used.

The response message returned by the endpoint 1901 is a SIP 200 OKmessage that may include the tag extracted from the received INFOmessage to identify which of the routes was successful (e.g., whichroute carried the message that was received first). For purposes ofexample, the private route was successful and the table may then beupdated as shown in Table 2 below:

TABLE 2 Buddy Endpoint Route (send-receive) 1901 pr-unk X X X X

It is noted that since the private route is successful, the twoendpoints 104 and 1901 are in the same private network.

It is understood that the response message (e.g., the SIP 200 OK) maynever be received by the endpoint 104. For example, the private routemay not be available from the endpoint 1901 to the endpoint 104 due tonetwork configuration settings. Accordingly, if the SIP 200 OK is notreceived by the endpoint 104, the endpoint 104 may execute aretransmission process that resends the presence messages along thethree routes. The resending may occur a set number of times, for a setperiod of time, or until some other limit is reached. For example, thefirst set of presence messages may be sent 0.5 seconds after the initialmessages are sent, the second set of messages may be sent one secondafter that, and each additional set of messages may be sent at timeperiods that are double the previous delay until a total of seven setsof messages are sent. At this time, the endpoint 104 may stop sendingmessages. If a response is received during the retransmission process,the endpoint 104 will stop retransmitting. However, the response messagewill generally be received by the endpoint 104.

The outbound SIP INFO messages and the received SIP 200 OK messageinform the endpoint 104 of which route to use when sendingcommunications to the endpoint 1901. However, this route may not work inreverse. In other words, just because the endpoint 104 can reach theendpoint 1901 via the private route (to continue the example), it doesnot necessarily follow that the endpoint 1901 can reach the endpoint 104using the same route. For example, differences in the configurations ofNAT devices or other network differences may mean one endpoint can bereached via a particular route even if the reverse route is notavailable.

Accordingly, the endpoint 1901 sends out three presence messages insteps 2112, 2114, and 2116. As the current example uses SIP messagingtransported via UDP, the message is a SIP INFO message. Morespecifically, in step 2112, the endpoint 1901 sends a SIP INFO messageto the private IP address/port pair of the endpoint 104 (i.e., via theprivate route). In step 2114, the endpoint 1901 sends a SIP INFO messageto the public (NAT) IP address/port pair of the endpoint 104 (i.e., viathe public route). In step 2116, the endpoint 1901 sends a SIP INFOmessage to the endpoint 104 via the reflector 1002 (i.e., via the relayroute), which is reflected to the endpoint 104 in step 2118.

The present example assumes that the endpoint 104 receives one or moreof the messages sent in steps 2112, 2114, and 2116. If more than onemessage is received, the endpoint 104 may respond only to the first onereceived. Accordingly, only one of steps 2120A, 2120B, and 2120C-1 mayoccur in the present example. Step 2120C-2 is dependent on theoccurrence of step 2120C-1 because the response message will not bereflected unless the relay route is used. The response message returnedby the endpoint 104 is a SIP 200 OK message that identifies which of theroutes was successful (e.g., was received first).

If the first (or only) SIP INFO message received by the endpoint 104from the endpoint 1901 is received via the same route as that used bythe endpoint 104 to send messages to the endpoint 1901 (e.g., theprivate route), then the communication session is established withmessages going both ways on that route. At this point, the table maythen be updated as shown in Table 3 below:

TABLE 3 Buddy Endpoint Route (send-receive) 1901 pr-pr X X X X

However, the first (or only) SIP INFO message received by the endpoint104 from the endpoint 1901 may be received on a different route thanthat used by the endpoint 104 to send messages to the endpoint 1901.When this occurs, the endpoint 104 flags this as the endpoint 1901responded to the INFO message via one route but is now communicating viaanother route. For example, the endpoint 1901 responded on the privateroute, but is now using the public route. One possibility for thisdiscrepancy is that there is a router or other network deviceinterfering with the return path (i.e., the path used by the endpoint1901 to send messages to the endpoint 104). Another possibility is thata message went faster one way than another way. For example, while theendpoint 1901 may have received the private message from the endpoint104 (i.e., the message of step 2102 of FIG. 21) before the othermessages, the endpoint 104 may have received the public message from theendpoint 1901 (i.e., the message of step 2114 of FIG. 21) before thepublic and relay messages.

When this occurs, the endpoint 104 may transition from the private routeto the public route. This results in sending and receiving routes ofpu-pu as illustrated by Table 4 below:

TABLE 4 Buddy Endpoint Route (send-receive) 1901 pu-pu X X X X

The endpoint 104 may also be configured to confirm that this transitionis correct. To confirm the transition, the endpoint 104 executes aconfirmation process and sends a confirmation message to the endpoint1901 on the private route (i.e., the route that the endpoint 104 thinksit should be using to send messages to the endpoint 1901). In thepresent example, the confirmation message may include a SIP field namedMAX_FORWARDS that defines a maximum number of hops that a packet cantake before being dropped. The MAX_FORWARDS field has a standard defaultvalue of seventy, but the endpoint 104 may set the value to one (i.e.,MAX_FORWARDS=1). If the response message from the endpoint 1901 isreceived by the endpoint 104 and has set the MAX_FORWARDS field to 0,then the endpoint 104 transitions back to the private route and usesthat route for sending future messages. This results in differentsending and receiving routes as illustrated by Table 5 below:

TABLE 5 Buddy Endpoint Route (send-receive) 1901 pr-pu X X X X

However, if the endpoint 104 does not receive a response message to itsconfirmation message, it continues using the public route. This resultsin sending and receiving routes of pu-pu as illustrated by Table 4above.

Communications between the endpoints 104 and 106 as illustrated in FIG.19B may follow the same sequence of presence messages and responses asthat described above with respect to FIGS. 20 and 21. However, since theendpoints 104 and 106 are in separate networks (i.e., not the same localnetwork), the private route 1902 is not available and the privatepresence messages will fail to reach their destination. The presencemessages may still be sent each way on the private route as theendpoints 104 and 106 do not know the location of the other endpoint,but the messages will be dropped. For example, the NAT devices 1004 and1006 may both be routers that have an address of 192.168.1.1 in theirrespective home networks. The NAT device 1004 may assign a privateaddress of 192.168.1.10 to the endpoint 104 and the NAT device 1006 mayassign a private address of 192.168.1.15 to the endpoint 106. Althoughthese addresses appear to be in the same local network, they are not.However, as the endpoints 104 and 106 have no way of knowing whether theprivate addresses are in the same local network until they perform theirstrategic routing sequences, they may both send their private presencemessages along the private route, even though the messages will bothfail. Accordingly, the endpoints 104 and 106 will use the public route1904 and/or the relay route 1906 when communicating.

Referring to FIG. 22, a flowchart illustrates one embodiment of a method2200 that may represent a process by which an endpoint such as theendpoint 104 of FIGS. 19A and 19B establishes a connection with anotherendpoint as described with respect to FIGS. 20 and 21 above.

In step 2202, the endpoint 104 sends outbound presence messages on theprivate, public, and relay routes. The presence messages may containidentifiers such as tags or other route indicators, or the receivingendpoint may simply note which virtual interface (i.e., pr, pu, or rl)received a particular presence message and correlate the message withthe route upon receipt. In step 2204, the endpoint 104 receives aresponse message that indicates which of the presence messages wasreceived first. For example, the response message may include the tagfrom the presence message to identify the route corresponding to thereceived presence message. In step 2206, the endpoint 104 selects theidentified route as the initial outbound route for messages being sentto the other endpoint.

In step 2208, the endpoint receives one or more inbound presencemessages from the other endpoint. In step 2210, the endpoint 104 sends aresponse to the first received inbound presence message.

In step 2212, the endpoint 104 determines whether the inbound route ofthe message received in step 2210 is the same route as the initialoutbound route selected in step 2206. If the routes are the same, themethod 2200 continues to step 2220 and uses the initial outbound routeto send messages to the other endpoint. If the routes are not the same,the method 2200 moves to step 2214 and sends a confirmation message tothe other endpoint using only the initial outbound route. In step 2216,the endpoint 104 determines whether a response to the confirmationmessage has been received. If no response to the confirmation messagehas been received, the method 2200 moves to step 2218 and transitions tothe inbound route as the new outbound route for messages being sent tothe other endpoint. If a response to the confirmation message has beenreceived, the method 2200 continues to step 2220 and uses the initialoutbound route to send messages to the other endpoint.

In step 2222, the endpoint 104 may begin sending keep-alive messages tothe other endpoint to ensure that the outbound route remains open. Forexample, one of the networks or NAT devices involved in the establishedsession may undergo a configuration change or a failure while the twoendpoints are online, and so an existing route may become unusable. Insuch a case, the endpoint may detect that the keep-alive messages arefailing and so may return to step 2202 to re-establish a valid route. Itis noted that the other endpoint may not need to re-establish itsoutbound route. For example, if the inbound and outbound routes for theendpoint 104 are different, the inbound route may remain valid eventhough the outbound route is invalid. Accordingly, some steps of themethod 2200 may be skipped in some scenarios.

It is noted that many different variations of the method 2200 may exist.For example, the endpoint 104 may transition to the inbound route as thenew outbound route if it is determined in step 2212 that the routes arenot the same, rather than remaining on the initial outbound route. Then,if a response is received to the confirmation message, the endpoint 104may transition back to the initial outbound virtual interface.Furthermore, as stated previously, the response message may never bereceived by the endpoint 104 and so some steps of the method 2200 maynot occur or may occur in a different order as there may be no responsemessage available to determine the initial outbound route. It is alsonoted that some steps of the method 2200 may be performed in a differentorder than shown. For example, step 2208 may occur before step 2204depending on network latency and other factors.

Referring to FIGS. 23A and 23B, in another embodiment, the endpoints 104and 106, the two NAT devices 1004 and 1006, and the stateless reflector1002 of FIGS. 19A and 19B are illustrated with a tunneling server orother access device 2302 and another endpoint 2304. The tunneling server2402 may provide access to other endpoints for an endpoint that does nothave UDP access or access to another expected protocol. For example, ifthe endpoint 104 performs a STUN request and the request fails, thenetwork within which the endpoint 104 is positioned may not support UDP(e.g., the network may be an Enterprise network that has disabled UDP).For purposes of illustration, the endpoints 104 and 2304 are in aprivate network and not separated by the NAT device 1004, and theendpoint 106 is separated from the endpoint 104 by the NAT devices 1004and 1006.

Referring to FIG. 24, a sequence diagram illustrates one embodiment of amessage sequence 2400 that may occur in the environment of FIGS. 23A and23B to establish a connection between the endpoints 104 and 106. As withthe previous discussion of FIG. 20, the endpoints 104 and 106 may eachmaintain a table, although this is not shown in the present example.

In step 2402, the endpoint 104 sends a STUN request that fails. Based onthe failure of the STUN request, the endpoint 104 determines that thenetwork (e.g., the NAT device 1004) has disabled UDP. It is understoodthat other indicators may be used to determine that UDP is notavailable. In step 2404, based on the unavailability of UDP, theendpoint 104 opens a TCP/IP connection (i.e., a tunnel) with thetunneling server 2302. This connection may use a port such as port 443of the NAT device 1004, which is the default TCP port for HTTP Secure(HTTPS) connections using the Transport Layer Security (TLS) or SecureSocket Layer (SSL) protocols. However, it is understood that port 443 isonly an example and that other available ports may be used. In step2406, the endpoint 104 requests a shadow IP address and shadow port onthe tunneling server 2302. In step 2408, the tunneling server 2302creates the shadow IP address and port and returns this information tothe endpoint 104 in step 2410.

The shadow IP address and shadow port serve as the public address andport of the endpoint 104 for other endpoints. In other words, the shadowIP address/port replace the NAT IP address/port that would serve as thepublic contact information for the endpoint 104 in an environment inwhich UDP is available to the endpoint 104 (e.g., as in FIGS. 19A and19B). In some embodiments, the shadow IP address/port pairs may beplaced on a shadow list as they are provisioned and the shadow list maybe available to the access server 102 and/or endpoints. In otherembodiments, the access server 102 and/or endpoints may have a list orrange of IP addresses/ports that are known to be shadows. In still otherembodiments, the knowledge of whether an IP address/port is a shadow isnot available to the access server 102 and/or endpoints.

In step 2412, the endpoint 104 authenticates with the access server 102via the tunnel using its local IP address/port and shadow address/portinformation. In step 2414, the access server 102 authenticates theendpoint 104 and sends the endpoint 104 the contact information ofonline buddies, including corresponding private, public, and shadow IPaddress/port information.

Although not shown in FIG. 24, the endpoint 106 sends a request to aSTUN server and receives its public IP address/port information asdescribed with respect to the endpoints 104 and 1901 in FIG. 20. Sincethe endpoint 106 is successful with its STUN request, it does not needto use the tunneling server 2302. In steps 2416 and 2418, the endpoint106 authenticates with the access server and receives the private IPaddress/port and shadow IP address/port of the endpoint 104. Asdiscussed above, the endpoint 106 may or may not know that the endpoint104 is using a shadow, depending on the particular implementation of theshadow list.

In steps 2420 and 2422, the endpoints 104 and 106 may establish acommunication session as described previously with respect to FIGS. 20and 21. However, the communications between the two endpoints 104 and106 will use the tunnel between the endpoint 104 and the tunnelingserver 2302 and the corresponding shadow IP address and port for theendpoint 104.

In embodiments where the endpoint 106 knows that the endpoint 104 isusing a shadow, the endpoint 106 may not send a presence message via theprivate route as the endpoint 106 knows that the private route is notavailable. In other embodiments, the endpoint 106 may send a presencemessage via the private route even though the route is not available.

Communications between the endpoints 104 and 2304 as illustrated in FIG.23B may follow a similar sequence of presence messages and responses asthat described above with respect to FIG. 24. However, since theendpoints 104 and 2304 are in the same local network, the private route1902 is available and the private presence messages may reach theirdestinations. The endpoint 2304 may not use a relay message to try toreach the endpoint 104, since its failed STUN request will inform theendpoint 2304 that UDP is not available. In order to use the public andrelay routes, the endpoint 2304 will create a tunnel with the tunnelingserver 2303 as described above with respect to the endpoint 104. Thepublic and relay messages may still work via the respective tunnels ofthe endpoints 104 and 2304.

Referring to FIG. 25, in another embodiment, the endpoints 104 and 106,the NAT device 1004, and the tunneling server 2302 of FIGS. 23A and 23Bare illustrated with another endpoint 2502. For purposes ofillustration, the endpoints 104, 106, and 2502 are all in separatenetworks and are unable to communicate using the private routepreviously described. The endpoints 104 and 2502 are behind the NATdevice 1004 and a NAT device 2504, respectively, both of which block UDPaccess to endpoints that are external to their respective network. Theendpoint 106 may not have a NAT device separating it from the externalendpoints or, in some embodiments, the NAT device may be present butconfigured to allow access without restricting communications (e.g., mayprovide functionality such as virus scanning without performing othermessage filtering and/or port blocking). Although the endpoint 104 isillustrated with two public interfaces (pu1 and pu2) and no relay orprivate interfaces, this is for purposes of clarity only and it isunderstood that the endpoint 104 may have additional interfaces that arenot shown, such as the relay and private interfaces described inprevious embodiments.

As described previously, tunnels may be used by endpoints to communicatedespite UDP blocking by NAT devices. Accordingly, the endpoints 104 and2502 may create tunnels in order to communicate despite the UDP blockingperformed by the NAT devices 1004 and 2504 respectively. In the presentembodiment, the endpoint 104 establishes tunnels 2506 and 2508 with thetunneling server 2302 and the endpoint 2502 establishes tunnels 2510.Although shown as a single tunnel, it is understood that each of thetunnels 2506, 2508, and 2510 may be multiple tunnels. Each of thetunnels 2506, 2508, and 2510 corresponds to a shadow IP address andports on the tunneling server 2302. For example, the tunnels 2506correspond to shadow IP address and ports 2512, the tunnels 2508correspond to shadow IP address and ports 2514, and the tunnels 2510correspond to shadow IP address and ports 2516.

The tunnels 2506 provide a path 2518 between the endpoint 104 and thetunneling server 2302. The path 2518 is coupled to a path 2522 betweenthe endpoint 106 and the tunneling server 2302 by a path 2520 that isinternal to the tunneling server 2302. For example, the path 2520 mayinclude one or more buffers and internal communication paths coupled toone or more communication interfaces for receiving, buffering, andsending signaling and data information. The tunnels 2508 provide a path2524 between the endpoint 104 and the tunneling server 2302. The tunnels2510 provide a path 2528 between the endpoint 2502 and the tunnelingserver 2302. The paths 2524 and 2528 are coupled by a path 2526 that isinternal to the tunneling server 2302. For example, the path 2526 mayinclude one or more buffers and internal communication paths coupled toone or more communication interfaces for receiving, buffering, andsending signaling and data information.

Referring to FIG. 26, a sequence diagram illustrates one embodiment of amessage sequence 2600 that may occur in the environment of FIG. 25 toestablish connections between the endpoints 104, 106, and 2502, and thetunneling server 2302. As with the previous discussion of FIG. 20, theendpoints 104, 106, and 2502 may each maintain a table, although this isnot shown in the present example. For purposes of example, the messagesequence 2600 represents possible messaging that may occur whileestablishing a connection by the endpoint 104 with the endpoint 106.

In step 2602, the endpoint 104 sends a request message to the reflector1002. The endpoint 104 may then start a timer in step 2604 to avoidwaiting indefinitely for a response from the reflector 1002. In thepresent example, as indicated in step 2606, the endpoint 104 does notreceive a response to the request from the reflector 1002. Although FIG.26 shows that the response of step 2606 fails, it is understood that therequest of step 2602 may not reach the reflector 1002 and step 2606 maynot occur. Regardless of whether the request of step 2602 reaches thereflector 1002, the timer of the endpoint 104 expires in the presentexample without a response being received by the endpoint 104.

In step 2608, after determining that the UDP path failed based on theexpiration of the timer, the endpoint 104 opens a TCP/IP connection withthe tunneling server 2302 and, in step 2610, requests remote signalingand media ports. In the present example, the endpoint 104 requests afirst remote port for signaling and one or more additional remote portsfor media. As described previously, these remote ports are shadow portsthat represent the endpoint 104 on external networks, such as thenetwork in which the endpoint 106 is located. In step 2612, thetunneling server 2302 creates the shadow ports and, in step 2614,returns the shadow IP address and shadow ports to the endpoint 104.

In steps 2616 and 2618, the endpoint 104 communicates with the endpoint106 using a first shadow port (e.g., shadow port #1) for signaling andone or more other shadow ports (e.g., shadow ports #2 and up) for media.As will be described below in greater detail, the signaling and mediamessaging occur on separate tunnels in the present embodiment. Invites,buddy requests, streaming media (e.g., audio and/or video), call setupand teardown, online status information, and any other type of message,whether streaming or not, may be sent via the appropriate one of thetunnels 2506.

Although not shown, the tunnels 2508 and 2510 may be established in asimilar manner by the endpoints 104 and 2502, respectively, in order tocommunicate with one another. It is understood that if the endpoints 104and 2502 were in the same network (as shown by the endpoints 104 and2304 of FIG. 23B), they could communicate using the private interfacewithout needing the tunneling server 2302. Furthermore, the endpoint 104may have different routes operating simultaneously, such as one or moreprivate, public, and relay routes.

Referring to FIG. 27, in another embodiment, the endpoints 104 and 106and the tunneling server 2302 are illustrated with the tunnels 2506divided into three tunnels 2702, 2704, and 2706. The three tunnels 2702,2704, and 2706 may carry different message types, such as the tunnel2702 being used for signaling, the tunnel 2704 being used for video, andthe tunnel 2706 being used for audio. The shadow ports 2512 areillustrated as three shadow ports 2708, 2710, and 2712 and correspond tothe tunnels 2702, 2704, and 2706, respectively. It is understood thatthe paths 2518, 2520, and 2522 represent a path between the publicinterface pu1 of the endpoint 104 and the public interface pu of theendpoint 106. However, one or more of the paths 2518, 2520, and 2522 maybe divided into one or more physically and/or logically separate paths.For example, the path 2520 within the tunneling server 2302 may bedivided into physically separate paths that are coupled to differentbuffers associated with ports 2708, 2710, and 2712.

Referring to FIG. 28, in another embodiment, a flowchart illustrates oneembodiment of a method 2800 that may represent a process by which atunneling server such as the tunneling server of FIGS. 25 and 27 handlescommunication between endpoints such as the endpoints 104, 106, and2502. As will be described, the tunneling server 2302 may handlecommunications between the endpoints 104 and 2502 internally and betweenthe endpoints 104 and 106 using shadow ports. In previously describedFIG. 23B, the tunneling server 2302 is illustrated as handlingcommunications occurring between the public interfaces of the endpoints104 and 2304 using shadow ports. However, such communications may behandled internally by the tunneling server 2302. In the present example,the method 2800 is directed to establishing tunnels with the endpoint104 for communication with the endpoint 106. However, it is understoodthat it may be applied to establishing any tunnel such as the tunnels2506, 2508, and 2510 for communication with any other endpoint.

In step 2802, the tunneling server 2302 establishes a TCP/IP connectionwith the endpoint 104 in response to a connection request from theendpoint 104. In step 2804, the tunneling server 2302 receives a requestfrom the endpoint 104 for shadow ports. For purposes of continuing theexample of FIG. 27, the tunneling server receives a request for threeshadow ports that will correspond to tunnels 2702, 2704, and 2706 whencreated. In step 2806, the tunneling server 2302 attempts to create theshadow ports and, in step 2808, a determination is made as to whetherthe shadow ports were successfully created. For example, the tunnelingserver 2302 may not have enough available ports to fulfill the request.If the attempt to create the shadow ports is not successful, thetunneling server 2302 sends a failure notification to the endpoint 104in step 2810. If the shadow ports are successfully created, the method2800 moves to step 2812 and sends the shadow IP address and shadow portinformation to the endpoint 104 in step 2812.

In step 2814, the tunneling server 2302 receives a message from theendpoint 104 and extracts the destination IP address and portinformation from the message. In step 2816, a determination is made asto whether the destination IP address is the same as the IP address ofthe tunneling server 2302. If the two IP addresses are not the same, thetunneling server 2302 sends the message to the destination IPaddress/port identified from the message. For example, the extracted IPaddress and port information may correspond to the endpoint 106. As theIP address of the endpoint 106 does not match the IP address of thetunneling server 2302, the tunneling server 2302 will send the messageto the endpoint 106.

In step 2820, if the two IP addresses are the same, a determination maybe made as to whether there is an endpoint associated with thedestination port on the tunneling server 2302. More specifically,identical IP addresses may indicate that the destination is a shadowport on the tunneling server 2302. If the destination is a shadow porton the tunneling server 2302, then the destination endpoint is connectedto the tunneling server 2302 via a tunnel (e.g., the endpoint 2502 viathe tunnel 2510). Accordingly, the tunneling server 2302 may determinewhether the destination port is valid by determining whether there is anendpoint associated with that port. In step 2822, if there is anendpoint associated with that port, then the tunneling server 2302 maymove the message internally to that port rather than sending it out asillustrated by path 1904 of FIG. 25B. For example, the tunneling server2302 may move the message from an inbound buffer to the outbound bufferfor that port. In step 2824, if there is no endpoint currentlyassociated with that port, the tunneling server 2302 may send a messageto the endpoint 104 indicating that the message cannot be delivered.

Although not shown in FIG. 28, it is understood that the tunnelingserver 2302 may take additional steps. For example, the tunneling server2302 may notify the access server 102 of the shadow ports correspondingto the endpoint 104, may publish the shadow port information, and/or mayperform additional steps to aid in communication within the peer-to-peerhybrid network. Furthermore, in some embodiments there may multipletunneling servers. In such embodiments, if the tunneling server 2302does not have enough available ports for the endpoint 104, the tunnelingserver 2302 may notify the endpoint 104 that another tunneling serverhas available ports and provide the other server's address information.In still other embodiments, the endpoint 104 may receive suchinformation from the access server 102, from publication broadcasts fromthe tunneling servers, or from other sources. Accordingly, it isunderstood that many different network configurations of tunnelingservers may be used to provide tunneling for endpoint such as theendpoint 104.

It is understood that shadow ports may be created for each request evenif the shadow ports are not used. For example, as illustrated in FIG.25, the tunneling server 2302 may create shadows ports 2514 and 2516corresponding to tunnels 2508 and 2510, respectively, even though theseshadow ports are not used. Accordingly, in some embodiments, thetunneling server 2302 may identify that both endpoints (e.g., theendpoints 104 and 2502) are communicating via tunnels to the tunnelingserver 2302 and may release the shadow ports for use by other endpoints.In still other embodiments, shadow ports may remain until thecorresponding tunnel is broken down.

Referring to FIGS. 29A and 29B, systems 2900 and 2906, respectively,illustrate two embodiments of connection configurations with one or moreof the tunneling servers 2302 of FIG. 25. In the present examples, thetunneling server 2302 includes UDP/TCP bridge functionality. It isunderstood that the illustrated UDP and TCP connections representconnection types and do not necessarily represent actual physicalconnections. Accordingly, multiple distinct tunnels (e.g., the tunnels2702, 2704, and 2706 of FIG. 27) may be represented by a singleconnection in FIGS. 29A and 29B. It is also understood that one or moreof the illustrated connection configurations may be present. Forexample, the tunneling server 2302 may be using all of the illustratedconnection configurations simultaneously, and multiple configurations ofthe same type may be present.

In FIG. 29A, two different connection configurations are illustrated.One connection configuration 2902 uses a TCP-TCP connection between theendpoint 104 and the tunneling server 2302 and another TCP-TCPconnection between the tunneling server 2302 and the endpoint 106. Thisconnection configuration may occur, for example, when the endpoints 104and 106 are each connected to the tunneling server 2302 via TCP tunnelsas described in previous embodiments. Another connection configuration2904 uses a TCP-TCP connection between the endpoint 104 and thetunneling server 2302 and a UDP-UDP connection between the tunnelingserver 2302 and the endpoint 106. This connection configuration mayoccur, for example, when the endpoint 104 is connected to the tunnelingserver 2302 via a TCP tunnel and the endpoint 106 is connected to thetunneling server 2302 using UDP (e.g., when there is no NAT deviceblocking the UDP messaging and no TCP tunnel is needed).

In FIG. 29B, two different connection configurations are illustratedwith two tunneling servers 2302 a and 2302 b. The two tunneling servers2302 a and 2302 b may be on the same network or may be on differentnetworks. For example, when the two tunneling servers 2302 a and 2302 bare on the same network, an endpoint such as the endpoint 104 may log invia a tunnel to one tunneling server and may use another tunnelingserver for media or other requests. Furthermore, the two endpoints 104and 106 may use separate tunneling servers whether on the same network(if the network has more than one tunneling server) or differentnetworks.

One connection configuration 2908 uses a TCP-TCP connection between theendpoint 104 and the tunneling server 2302 a, a TCP-TCP connectionbetween the tunneling servers 2302 a and 2302 b, and a TCP-TCP and/or aUDP-UDP connection between the tunneling server 2302 b and the endpoint106. This connection configuration may occur, for example, when theendpoint 104 is connected to the tunneling server 2302 a via a TCPtunnel as described in previous embodiments, the two tunneling servers2302 a and 2302 b communicate with one another via TCP, and the endpoint106 is connected to the tunneling server 2302 b with a tunnel (TCP)and/or using UDP (e.g., when there is no NAT device blocking the UDPmessaging and no TCP tunnel is needed).

Another connection configuration 2910 uses a TCP-TCP connection betweenthe endpoint 104 and the tunneling server 2302 a, a UDP-UDP connectionbetween the tunneling servers 2302 a and 2302 b, and a TCP-TCP and/orUDP connection between the tunneling server 2302 b and the endpoint 106.This connection configuration may occur, for example, when the endpoint104 is connected to the tunneling server 2302 a via a TCP tunnel asdescribed in previous embodiments, the two tunneling servers 2302 a and2302 b communicate with one another via UDP, and the endpoint 106 isconnected to the tunneling server 2302 b with a tunnel (TCP) and/orusing UDP (e.g., when there is no NAT device blocking the UDP messagingand no TCP tunnel is needed).

Furthermore, as illustrated in FIG. 29B, the tunneling server 2302 b maybifurcate different message types and then recombine them prior tosending them out via a shadow port on the tunneling server 2302 b. Forexample, the tunneling server 2302 b may split the messages based ontype or based on another tag and send some messages to the endpoint 106via TCP and other messages to the endpoint 106 via UDP. In otherembodiments, the tunneling server 2302 b may send some or all messagesvia TCP, may send some or all messages via UDP, or may use one or moreother protocols. Although not shown, it is understood that a singlemessage type may be switched (e.g., UDP to TCP and/or TCP to UDP) in thesame manner.

Although shown with UDP and TCP, it is understood that the tunnelingserver 2302 of FIG. 29A and tunneling servers 2302 a and 2302 b of FIG.29B may be configured for use with other protocols. Accordingly, thepresent descriptions are not limited to UDP and TCP, but may be extendedor otherwise configured to provide tunneling and other communicationassistance based on desired message types and/or networks.

Referring to FIG. 30, one embodiment of a computer system 3000 isillustrated. The computer system 3000 is one possible example of asystem component or device such as an endpoint, an access server, or atunneling server. The computer system 3000 may include a centralprocessing unit (“CPU”) 3002, a memory unit 3004, an input/output(“I/O”) device 3006, and a network interface 3008. The components 3002,3004, 3006, and 3008 are interconnected by a transport system (e.g., abus) 3010. A power supply (PS) 3012 may provide power to components ofthe computer system 3000, such as the CPU 3002 and memory unit 3004. Itis understood that the computer system 3000 may be differentlyconfigured and that each of the listed components may actually representseveral different components. For example, the CPU 3002 may actuallyrepresent a multi-processor or a distributed processing system; thememory unit 3004 may include different levels of cache memory, mainmemory, hard disks, and remote storage locations; the I/O device 3006may include monitors, keyboards, and the like; and the network interface3008 may include one or more network cards providing one or more wiredand/or wireless connections to the packet network 108 (FIG. 1).Therefore, a wide range of flexibility is anticipated in theconfiguration of the computer system 3000.

The computer system 3000 may use any operating system (or multipleoperating systems), including various versions of operating systemsprovided by Microsoft (such as WINDOWS), Apple (such as Mac OS X), UNIX,and LINUX, and may include operating systems specifically developed forhandheld devices, personal computers, and servers depending on the useof the computer system 3000. The operating system, as well as otherinstructions (e.g., for the endpoint engine 252 of FIG. 2 if anendpoint), may be stored in the memory unit 3004 and executed by theprocessor 3002. For example, if the computer system 3000 is the endpoint104, the memory unit 3004 may include instructions for sending andreceiving messages to the tunneling server 2302 and other endpoints suchas the endpoints 106 and 2502.

In another embodiment, a method for establishing a peer-to-peercommunication session between first and second endpoints comprisesdetermining, by a first endpoint, that a first message protocol is notavailable for use in sending a first message to the second endpoint,wherein the determining identifies that none of a private interface, apublic interface, and a relay interface of the first endpoint areavailable when using the first message protocol, and wherein the privateinterface corresponds to a local address assigned to the first endpointby a network address translation (NAT) device in a local network, thepublic interface corresponds to a public address of the NAT device thatrepresents the first endpoint in networks outside of the local network,and the relay interface corresponds to a reflector located outside ofthe local network, and wherein the NAT device blocks the first messageprotocol; sending, by the first endpoint, a request for a firstconnection with a tunneling server, wherein the first connection isbased on a second message protocol allowed by the NAT device andprovides a first tunnel between the first endpoint and the tunnelingserver; sending, by the first endpoint, a request to the tunnelingserver via the first tunnel for at least first and second shadow portson the tunneling server; receiving, by the first endpoint, a shadowInternet Protocol (IP) address and the first and second shadow portsfrom the tunneling server via the first tunnel; and sending, by thefirst endpoint, a first message to the second endpoint via the firsttunnel. The connection with the tunneling server may use the publicinterface of the first endpoint. The method may further comprisesending, by the first endpoint, a request for a second connection withthe tunneling server, wherein the second connection is based on thesecond message protocol and provides a second tunnel between the firstendpoint and the tunneling server; and sending, by the first endpoint, athird message to the second endpoint via the second tunnel. The firstmessage may contain signaling information and the second messagecontains media information. The first message protocol may be UserDatagram Protocol (UDP) and the second message protocol may beTransmission Control Protocol/Internet Protocol (TCP/IP). Thedetermining may include sending, by the first endpoint, a third messageto a network component that is located on the opposite side of the NATdevice from the first endpoint and outside of the local network;monitoring, by the first endpoint, a timer; and determining that thefirst message protocol is not available when the timer expires and noresponse to the third message has been received by the first endpoint.The method may further comprise sending, by the first endpoint, apresence message to a third endpoint via the private interface, whereinthe presence message includes an identifier corresponding to the privateinterface and wherein the third endpoint is positioned in the localnetwork; receiving, by the first endpoint, a response from the thirdendpoint to the presence message; and using, by the first endpoint, theprivate interface as an outbound route to send additional messages tothe third endpoint, wherein the outbound route does not go through thetunneling server. The first endpoint may not be aware that the thirdendpoint is in the local network when sending the presence message.

In another embodiment, a method for use by a tunneling server in apeer-to-peer hybrid network comprises establishing, by the tunnelingserver, a connection with a first endpoint in response to a connectionrequest from the first endpoint; receiving, by the tunneling server, arequest from the first endpoint for a plurality of shadow ports on thetunneling server; creating, by the tunneling server, the plurality ofshadow ports; sending, by the tunneling server, a shadow network addressand the shadow ports to the first endpoint; receiving, by the tunnelingserver, a message from the first endpoint; extracting, by the tunnelingserver, a destination network address and a destination port from themessage; determining, by the tunneling server, whether the destinationnetwork address matches a network address of the tunneling server; andsending, by the tunneling server, the message out of the tunnelingserver to a second endpoint corresponding to the destination networkaddress only if the destination network address does not match thenetwork address of the tunneling server. The method may further comprisedetermining, by the tunneling server, whether the destination port isassociated with a third endpoint if the destination network addressmatches the network address of the tunneling server; and moving, by thetunneling server, the message to a buffer internal to the tunnelingserver if the destination port is associated with the third endpoint,wherein the buffer corresponds to the endpoint associated with thedestination port and the message is not sent out of the tunnelingserver. The method may further comprise sending, by the tunnelingserver, a notification message to the first endpoint that the messagecannot be delivered if the destination network address matches thenetwork address of the tunneling server and the destination port is notassociated with an endpoint. The method may further comprise dropping,by the tunneling server, the message if the destination network addressmatches the network address of the tunneling server and the destinationport is not associated with an endpoint. The method may further comprisedetermining, by the tunneling server, that the third endpoint associatedwith the destination port is communicating with the first endpoint via atunnel between the third endpoint and the tunneling server; andreleasing, by the tunneling server, the shadow ports created for thefirst endpoint. The method may further comprise sending, by thetunneling server, a notification message to the first endpointidentifying another tunneling server available for use by the firstendpoint.

In still another embodiment, an endpoint comprises a network interface;a controller coupled to the network interface; and a memory coupled tothe controller, the memory having a plurality of instructions storedthereon for execution by the controller, the instructions includinginstructions for: determining whether a first message protocol isavailable for use in sending a first message to a second endpoint in ahybrid peer-to-peer network, wherein the determining identifies whetherany of a private interface, a public interface, and a relay interface ofthe first endpoint are available when using the first message protocol,and wherein the private interface corresponds to a local addressassigned to the first endpoint by a network address translation (NAT)device in a local network, the public interface corresponds to a publicaddress of the NAT device that represents the first endpoint in networksoutside of the local network, and the relay interface corresponds to areflector located outside of the local network; establishing a tunnelwith a tunneling server that is located outside of the local networkusing a second message protocol only if the first message protocol isnot available for use in sending the first message to the secondendpoint; obtaining a shadow address and a plurality of shadow portsfrom the tunneling server; sending the first message to the secondendpoint via the tunnel; and receiving a second message from the secondendpoint via the tunnel. The instructions for determining may includeinstructions for sending a third message to a network component that islocated on the opposite side of the NAT device from the first endpointand outside of the local network; and determining that the first messageprotocol is not available when a predefined event occurs and no responseto the third message has been received by the first endpoint. Theendpoint may further comprise instructions for: sending a presencemessage to a third endpoint via the private interface, wherein thepresence message includes an identifier corresponding to the privateinterface and wherein the third endpoint is positioned in the localnetwork; receiving, by the first endpoint, a response from the thirdendpoint to the presence message via the private interface; and using,by the first endpoint, the private interface as an outbound route tosend additional messages based on the first message protocol to thethird endpoint, wherein the outbound route does not go through thetunneling server. The endpoint may further comprise instructions forsending the presence message prior to determining whether the firstmessage protocol is available for use. The endpoint may further compriseinstructions for sending a presence message to the second endpoint viaeach of the private interface, public interface, and relay interface andwherein the determining is based on whether a response is received tothe presence message sent via the relay interface. The first messageprotocol may be User Datagram Protocol (UDP) and the second messageprotocol may be Transmission Control Protocol/Internet Protocol(TCP/IP).

While the preceding description shows and describes one or moreembodiments, it will be understood by those skilled in the art thatvarious changes in form and detail may be made therein without departingfrom the spirit and scope of the present disclosure. For example,various steps illustrated within a particular sequence diagram or flowchart may be combined or further divided. In addition, steps describedin one diagram or flow chart may be incorporated into another diagram orflow chart. Furthermore, the described functionality may be provided byhardware and/or software, and may be distributed or combined into asingle platform. Additionally, functionality described in a particularexample may be achieved in a manner different than that illustrated, butis still encompassed within the present disclosure. Therefore, theclaims should be interpreted in a broad manner, consistent with thepresent disclosure.

What is claimed is:
 1. A method for use by a tunneling server in a peer-to-peer hybrid network comprising: establishing, by the tunneling server, a connection with a first endpoint in response to a connection request from the first endpoint; receiving, by the tunneling server, a request from the first endpoint for a plurality of shadow ports on the tunneling server; creating, by the tunneling server, the plurality of shadow ports; sending, by the tunneling server, a shadow network address and the shadow ports to the first endpoint; receiving, by the tunneling server, a message from the first endpoint; extracting, by the tunneling server, a destination network address and a destination port from the message; determining, by the tunneling server, whether the destination network address matches a network address of the tunneling server, wherein a match indicates that the destination port is a shadow port on the tunneling server; and sending, by the tunneling server, the message out of the tunneling server to a second endpoint corresponding to the destination network address only if the destination network address does not match the network address of the tunneling server.
 2. The method of claim 1 further comprising: determining, by the tunneling server, whether the shadow port is associated with a third endpoint if the destination network address matches the network address of the tunneling server; and moving, by the tunneling server, the message to a buffer internal to the tunneling server if the shadow port is associated with the third endpoint, wherein the buffer corresponds to an endpoint associated with the destination port and the message is not sent out of the tunneling server.
 3. The method of claim 2 further comprising sending, by the tunneling server, a notification message to the first endpoint that the message cannot be delivered if the destination network address matches the network address of the tunneling server and the shadow port is not associated with an endpoint.
 4. The method of claim 3 further comprising dropping, by the tunneling server, the message if the destination network address matches the network address of the tunneling server and the shadow port is not associated with an endpoint.
 5. The method of claim 2 further comprising: determining, by the tunneling server, that the third endpoint associated with the shadow port is communicating with the first endpoint via a tunnel between the third endpoint and the tunneling server; and releasing, by the tunneling server, the shadow ports created for the first endpoint.
 6. The method of claim 1 further comprising sending, by the tunneling server, a notification message to the first endpoint identifying another tunneling server available for use by the first endpoint. 